1. Field of Invention
This invention relates to a winding mechanism for controlling the retraction and deployment of an architectural covering, especially a covering for an architectural opening, such as a window blind or shade. This invention particularly relates to a spring-assisted winding mechanism useful for controlling the winding and unwinding of the covering, itself, about a tubular roller or for controlling the winding and unwinding of lift cords and/or tapes of the covering about a spool or the like. This invention quite particularly relates to a fluid brake which can be used in such a winding mechanism to control the retraction or winding up of the covering or the lift cords or tapes.
2. Description of the Known Art
Winding mechanisms for retracting or raising window shades and blinds have often used a spring retraction mechanism to bias the shades and blinds towards their retracted position. To hold a shade or blind in its deployed or lowered position, these mechanisms have also been provided with a locking mechanism. Conventionally, the locking mechanism has involved an arrangement in which, when the shade or blind has been pulled down or unwound and then released, the shade or blind has been locked in the lowered position. If the shade or blind has been pulled down again, the locking mechanism has been released, and a spring retraction mechanism has caused the shade or blind to be retracted or rolled up again. Such roller mechanisms have been used, for example, for winding and unwinding roller blinds and lift cords of pleated blinds and roman shades. See EP 0 087 146.
Recently, there has been an increased demand for a device for retracting or braking the rotational speed of retraction of spring-assisted winding mechanisms of shades and blinds. Such rotational speed of retraction, if not smoothed or controlled, can cause shades and blinds to fly up and can easily damage their components when they are retracted. To avoid such damage, it has been proposed to use mechanical braking or retarding devices to obtain a continuous, smooth and controlled retraction of the blinds.
One such retarding device, described in EP 0 093 289, has used a pair of centrifugally-acting brake shoes inside a brake drum. To achieve the required centrifugal speed, an epicyclic gear train has been provided to speed up rotation of the assembly, upon which the brake shoes are mounted. However, because it is essentially a mechanical retarding device, the retarding device of EP 0 093 289 has been subject to friction and wear and thus has tended to become less effective over time.
An additional demand has been for a retarding device which is effective in only the direction of rotation for retracting the shades and blinds, in order not to interfere with unwinding or lowering them. This has also been achieved to some extent by means of the one-way helically-wound spring clutch used in the retarding device described in EP 0 093 289.
It has also been proposed, in DE-G-92 03 450, to use a fluid brake containing a liquid, the viscosity of which increases when it is subjected to increasing shear stresses, for retarding the rotational speed of retraction of spring-assisted winding mechanisms of shades and blinds.
In this regard, such a liquid (e.g., a silicon oil) has been provided in a fluid-tight cylindrical compartment within a roller, and a fixed centre shaft of the roller has been positioned axially within the compartment. Upon rapid rotation of the roller and compartment about the shaft when retracting a shade, the liquid is subjected to increased shear stress, causing its viscosity to increase and causing it to retard such rotation.
In accordance with this invention, a winding mechanism for controlling the retraction and deployment of an architectural covering, such as a window blind or shade, is provided having a winding element, about which the covering or its lift cord or tapes are wound and unwound with rotation of the winding element about a first axis of rotation, and a fluid brake for retarding the rotation of the winding element in at least one direction about the first axis; the fluid brake comprising a fluid-tight compartment containing a liquid and an impeller and wherein: the compartment and the impeller are adapted for relative rotation about a second axis of rotation; the compartment or the impeller is operatively connected to the winding element; the liquid rotates with rotation of the compartment or the impeller about the second axis; rotation of the liquid relative to the impeller or to the compartment in at least a first direction about the second axis is effective to retard the rotation of the winding element in at least a second direction about the first axis; and the impeller or an inner peripheral wall surface of the compartment has a first surface that extends generally radially and substantially parallel with respect to the second axis.
Preferably the first and second axes are coaxial, and advantageously the first and second directions are the same.
Advantageously the compartment is operatively connected to, and rotates with, the winding element and rotation of the liquid with the compartment, relative to the impeller, in at least the first direction about the second axis is effective to retard the rotation of the winding element in at least the second direction about the first axis. Advantageously, the fluid brake is within the winding element.
The liquid preferably has a viscosity that increases with increasing agitation of the liquid in the compartment.
In accordance with one embodiment of the invention, the first surface is on a vane eccentrically mounted on, and protruding axially from, a radially-extending disk of the impeller or is on a vane mounted on, and protruding radially from, a hub of the impeller, especially where: i) the inner peripheral wall surface of the compartment is generally cylindrical; ii) the impeller has a plurality of the vanes which are movable and can be flexible and resilient but are advantageously hingedly connected to the impeller; and iii) each vane also has a second surface that can be moved towards the inner peripheral wall surface when pressure is exerted by the liquid against the first surface of the vane. In this regard, it is particularly advantageous that the second surface of each vane can frictionally engage the inner peripheral wall surface of the compartment when pressure is exerted by the liquid against the first surface of the vane, especially where each vane has a curvilinear cross-section that is concave towards the first surface.
In accordance with another embodiment of the invention, the impeller does not rotate or rotates in the opposite direction from the rotation of the compartment about the second axis. In this regard, it is particularly advantageous that a one-way clutch be interposed between the winding element and the compartment or the impeller, especially where an inverting gear assembly, particularly a speed-up gear assembly, is interposed between the clutch and the compartment or the impeller. The speed-up gear assembly may comprise an epicyclic gear train having a sun gear, planet gear wheels and a ring gear; and wherein the impeller is connected to the sun gear, the planet gear wheels are rotatably carried by the one-way clutch, and the ring gear is connected to the winding element for rotation therewith.
It is also contemplated that the winding mechanism should further comprise: an elongate longitudinally-extending hollow roller extending along the first axis, having its opposite ends rotatably connected to a pair of bearing journals and having an end of the covering attached to it; a fixed element within the roller, connected to one of the bearing journals; and a spring-urged winding mechanism operatively connected to the fixed element and the roller and adapted to urge the roller to rotate in a first direction about the first axis to retract the covering; and wherein the fluid brake is within the roller, is operatively connected to the roller and the fixed element, and retards substantially only rotation of the roller in the first direction of rotation. In this regard, it is particularly advantageous that the compartment of the fluid brake be connected to the roller for rotation therewith.
In accordance with other aspects of the invention, an architectural covering, such as a window blind or shade, is provided comprising the winding mechanism just described, and a fluid brake is provided as just described.